Add queryMapEncoder to FeignClientProperties

[KENNYSOFT]

From #629 (comment)

[codecov]

Codecov Report

Merging #630 (bd46a10) into 3.0.x (c0f314a) will increase coverage by 0.73%.
The diff coverage is 71.42%.

@@             Coverage Diff              @@
##              3.0.x     #630      +/-   ##
============================================
+ Coverage     78.76%   79.50%   +0.73%     
- Complexity      519      538      +19     
============================================
  Files            62       65       +3     
  Lines          1898     1961      +63     
  Branches        270      273       +3     
============================================
+ Hits           1495     1559      +64     
- Misses          251      252       +1     
+ Partials        152      150       -2     

Impacted Files	Coverage Δ
...amework/cloud/openfeign/FeignClientProperties.java	86.91% <60.00%> (-0.47%)	⬇️
...mework/cloud/openfeign/FeignClientFactoryBean.java	77.99% <100.00%> (+3.67%)	⬆️
.../loadbalancer/FeignBlockingLoadBalancerClient.java	82.92% <0.00%> (-11.52%)	⬇️
...amework/cloud/openfeign/support/SpringEncoder.java	84.88% <0.00%> (-1.54%)	⬇️
...amework/cloud/openfeign/support/SpringDecoder.java	56.00% <0.00%> (-1.15%)	⬇️
...d/openfeign/hateoas/FeignHalAutoConfiguration.java	100.00% <0.00%> (ø)
...balancer/OkHttpFeignLoadBalancerConfiguration.java	100.00% <0.00%> (ø)
...alancer/DefaultFeignLoadBalancerConfiguration.java	100.00% <0.00%> (ø)
...ncer/HttpClientFeignLoadBalancerConfiguration.java	100.00% <0.00%> (ø)
...cer/HttpClient5FeignLoadBalancerConfiguration.java	100.00% <0.00%> (ø)
... and 16 more

[OlgaMaciaszek]

@KENNYSOFT Thanks for submitting the PR. It looks fine, however, more docs should have been added. Since we're planning to release 2021.0.1 today, I'm going to add them, in order to get this into the release.

[OlgaMaciaszek]

After a further consideration, although the code looks good, I don't see that it's a needed functionality - the general model of overriding these Feign configuration elements is via adding Java beans as also described in the documentation. Is there a scenario where that is causing an issue?
I'm going to leave this PR open to get opinions from the community, however, if no compelling reasons will be presented to add this, we'll stay just with the bean config option.

[KENNYSOFT]

Actually, Retryer, ErrorDecoder, and Capability are also supported via Java Bean with the way in application.yml. There are not any 'compelling reasons' but it can give more flexibility to set the QueryMapEncoder.

[KENNYSOFT]

Just found out fe8bbbb and integrated since v3.1.1; don't care whether it included in v3.0.x or not for now. Closing with thanks!